Seattle’s North Link Light Rail, Originally Considered for Highway-Running, May Be Partially Tunneled

» Underground route may actually save money — but it raises possibility of altering the alignment.

Seattle’s light rail expansion program may be one of the most ambitious in the nation: Not only did the region open a 14-mile first segment last year, but it has a northern extension currently under construction and three further routes mostly funded and in advanced planning. Unlike most new light rail systems, Seattle’s is also being built to light metro standards, with capacity for four (long) cars at every station.

This huge investment does not correlate with a perfectly planned system, of course. One of its major flaws is its reliance on the Interstate 5 right-of-way north of Seattle for the $1.4 billion, 4.3-mile North Link section of the project. It’s a route alignment that will not only restrict commuter access to and from stations, but also result in lessened transit-oriented development because of the limited appeal of locating new construction directly adjacent to a major highway. But the decision to stretch the light rail project along the side of the road was routed in the presumption that using an existing transportation corridor would save on land acquisition costs and allow expensive tunneling to be avoided.

Another 8.2-mile extension of the line, planned for the stretch from Northgate to Lynnwood, is currently suggested also to follow I-5 closely.

A new report from the region’s Sound Transit agency, however, suggests that moving trains underground could actually save money compared to the originally planned elevated alignment for a part of the route between the planned Roosevelt and Northgate Stations situated north of the University of Washington and the city center. If the engineers are correct, conventional wisdom about the high costs of tunneling made need to be reversed. The strict adherence to existing road rights-of-way that typically constrain new transit projects may need to give way to a broader vision of how new transit capacity can be built.

Current plans would extend the light rail tunnel from the University of Washington to 75th Street Northeast, where trains would exit onto an elevated route towards Northgate. Sound Transit’s new report suggests that the agency could save five to ten million dollars by extending the tunnel ten blocks further north — about half a mile — with the added benefit of reducing neighborhood environmental effects. Though the costs of tunneling have been reduced in recent years thanks to new boring methods, they’re rarely as cheap as transit built on the surface; this situation may prove to be an exception because it allows the light rail to avoid conflict with a number of road overpasses. And there are no planned stations along this stretch of track.

But the lesson is still worth considering more broadly speaking: As tunneling decreases in cost, the constraints that limit choices in rapid transit routes can be reduced and better alignments can be selected without damaging a project’s budget.

What the Seattle engineers are promoting now is merely a cost-saving solution to an expensive problem; it will keep the light rail in the I-5 right-of-way, just below it. Yet the realization that tunneling may actually be cheaper than building above ground raises questions about whether the city should continue to route the transit line along the Interstate alignment when other routes only accessible by underground tracks may be more appropriate for high-quality transit service.

It is probably too late to consider altering the alignment of North Link, since engineering is already underway, but it’s worth considering what could have been done differently in the stretch between Roosevelt and Northgate Stations had it been clear from the beginning that tunneling was a reasonable option.

The 2.3-mile distance between these two stations is a major concern; it puts a major population between the two out of easy walking distance to either station, reducing the appeal of the line and ridership prospects. The route along the highway left few desirable places for a third stop in between, but were trains routed under Roosevelt Way to the east of I-5 or under Aurora Avenue to the west of I-5, there are a number of areas that could support some increase in development coinciding with the arrival of rapid transit. Either of these routes would be a bit longer than the current alignment, but the added developmental activity resulting from their implementation could be enormous. Neither of these areas could have been served by ground-running trains because of limited street space.

Yet clear thinking about moving transit away from the highway right-of-way is only possible when it becomes obvious that the cost of inserting trains in tunnels is lower than other options. In Seattle, there is little chance that a wholehearted change in route is possible. But next time, either here or elsewhere, an underground route should not be dismissed as the “expensive,” and therefore infeasible, option.

I am very familiar with this part of Seattle, having lived in the area between the Roosevelt and Northgate station for 5 of the 7 years I was in Seattle (the other two years I lived right next door to where the University District station is going, on Brooklyn between NE 43rd and NE 45th).

I don’t share your concerns over the overall alignment between Roosevelt and Northgate. There aren’t all that many TOD opportunities between those two stations. A station at NE 75th and Roosevelt might have been workable, and it could be a good TOD location, but it’s fairly close to the Roosevelt station (at NE 65th and 12th Ave NE) so I’m not sure how much of a ridership boost would have been achieved.

Further up Roosevelt, there could be some TOD chances if you put a station at around NE 92nd. But even that might not bring enough ridership to justify the station or the considerable costs of tunneling under Maple Leaf hill. If you moved the route toward 5th Ave NE there’s even less good spots for TOD.

Northgate is quickly becoming a centerpiece of TOD in the Puget Sound region. I was just there about 3 months ago, after being away for over a year, and was stunned at how much TOD has already been built in anticipation of the light rail line, and even more is already under way.

North of there, the low-density and larger land plots mean you’d need to do some fairly radical surgery on the built environment to bring in some TOD. Which I’m fine with. Perhaps follow 5th Ave NE or bend over toward 15th Ave NE to put some stations at NE 145th/Jackson Park and NE 175th. But even then, an I-5 alignment isn’t that far away from those two north-south arterials. Depending on which side of the freeway you put the station, one could see some TOD for a block or two in the direction away from the freeway, especially at 5th Ave NE/NE 175th.

In short, though I usually share your skepticism at freeway alignments, in this particular instance I think it’s probably workable. Of more interest and consideration is what you do north of Lynnwood, toward Everett. Snohomish County could definitely use some TOD, and there should be plenty of opportunities north of the county line to break away from I-5 and build on a new alignment.

Well-said, Robert. The real TOD fight is not the Roosevelt-to-Northgate segment, which is well-designed and hits the critical neighborhoods. It is the question of the routing from Northgate to Lynnwood, currently planned for I-5 and very little TOD. The best route for TOD would be along Aurora, which could generate big ridership and help reshape Shoreline’s downtown.

Potential obstacles include a historically hostile Shoreline City Council (though the council may have shifted recently towards a more open-minded majority), the huge and expensive new park-and-ride on I-5 in Mountlake Terrace build in anticipation of light rail, and the fact that the funds in the Sound Transit 2 ballot measure package were determined assuming an I-5 route, though officially the project is still in the planning stages.

There is very little development opportunity along an I-5 route. The Sound Transit board needs to hear that a smarter alignment is a priority for the people of the Puget Sound region.

You missed the reason why it’s cheaper. The portal at 75th would have come out in a big I-5 interchange. Doing so would have required moving ramps and retaining walls in a dense, narrow corridor. The new portal at around 90th comes out in a big grassy freeway median. So it’s not so much that tunneling suddenly was cheaper, but it became cheaper and had fewer impacts than the alternative of moving a freeway 40′ west.

Subway tunnels are good in that they keep trains from mixing with street traffic. If a tunnel can save ten or 20 fender benders a year with a above rail line then it is money well spent. Also tunnels are cooler looking then above ground rail lines. A subway tunnel drilled though sold rock would also be something that could still be around hunderds of years after the subway line is built vs a EL which could fall apart over 50 years.

If you take the North Link and South Link projects to their logical conclusion, the train would eventually run from Tacoma to Everett, more than 60 miles. Assuming it’s someday well used, I would think even a light metro wouldn’t be able handle all the passengers that would come from it. This train even shares a downtown tunnel with buses. Is there something wrong with this?

Hmm. Well, there’s going to be a separate express route (Sounder) from Tacoma to Everett, which should relieve Link of much of its longer-distance traffic. There’s going to be some serious congestion in the central area however; I suppose they’ll eventually have to build a second line.

Sounder is peak period only and I doubt it will ever be more than a handful of trips each direction. It also misses much of the existing and potential residential/commercial density of the route. I’m fairly certain the bus ridership between Everett/Lynnwood/Mountlake Terrace and Seattle currently dwarfs the ridership of Sounder.

I don’t think you’ll see Sounder take much of the longer distance trips away from Link.

Wrong. Off-peak commuter rail service can make the peak service more attractive because it doesn’t tie people to specific hours. If the commuter rail only runs at peak hour, then riders may not take them if they’re not guaranteed to finish work before the last train leaves, even if it’s likely that they will; instead, they’ll drive.

The real capacity issue will be between Downtown Seattle and Northgate. Ultimately additional in-city lines will need to be built between Downtown and North Seattle, perhaps extending further North and East to Snohomish County and the East side of Lake Washington.

As for the buses in the downtown tunnel, they will be leaving as soon as there is no longer capacity for them. It is expected this will happen roughly about the same time Link opens all the way to Northgate.

@AlexB – the buses move up and out of the tunnel when the next segment to Husky Stadium opens around the middle of the decade. At 20 trains per hour with about 800 passengers per 4 car train max, LINK will be able to move as many folks in an hour as it is carrying in a day now.

Yeah it was going to come up out of a bored tunnel but to a mix of retained cut and cut-and-cover, not surface or elevated. Still, I see your point about the possibility of tunneling getting less expensive and more desirable in the coming years.

I agree with Mike B. There’s no basis for using this story to make any general claims that sometimes tunnelling is cheaper than surface. In this case, a tunnel that bypasses problematic spot turns out to be cheaper than a slightly shorter tunnel that puts you into that spot on the surface.

Surface can be expensive if you have big obstacles on the surface. That’s why we tunnel under steep hills. But all other things being equal, underground is still the most expensive profile option for rail transit, and always will be.

Note, too, that as soon as you start digging the risk of cost overruns goes way up. Seattle is sitting on complex volcanic geology with major seismic stresses. Sound Transit takes lots of core samples to understand what the rock is like where they are planning a tunnel, but there are still surprises, some of them expensive, when they start tunnelling.

Tunnel to get to somewhere really important, like Capitol Hill or the University, but otherwise stay on the surface if you can. That’s the only way Link will ever get to Lynnwood at all when you consider all the other transit needs in the region.

This situation is unique for this specific project and can’t really be used as an example/precedent for other systems. All they are is doing is extending a tunnel that they are already constructing…I have a hard time believing that constructing a new tunnel from scratch be cheaper that an elevated segment. That being said, it’s great to here that they are at least constantly analyzing what is proposed and looking for improvements. Ideally ST would utilize tunnels through all of the urban villages that link will serve as well as all choke-points through the region. I don’t think that the rainier segment is a fail but I think Interbay is an example of an area that you have to separate transit to get reliable service.

If its underground, shouldn’t Sound Transit then have the luxury of choosing the most optimal alignment with the highest ridership and best development opportunities?

I’m starting to wonder if underground routes aren’t so out of the question anymore. Yeah they are expensive, but it seems surface route costs are almost approaching that of tunneling with all the utility relocation, full street rebuilding, traffic and neighborhood impact mitigation, inefficient construction to accommodate merchants/traffic/neighbors, deluxe stations, etc.

What is worrisome in Seattle is that what is being built is not LRT or light rail at all but a very expensive light-metro or even worse a hybrid light rail/metro system combining both high cost and limited customer appeal.

The present daily ridership on the present line is an embarrassment compared to the vast cost of construction. At lest in Vancouver, people do take the SkyTrain light-metro, though 80% of the light-metro’s ridership first take a bus to SkyTrain.

The hysteria which comes with above ground LRT operation must make all civil engineers and cement company stock holders jump for joy as billions of dollars will be spent building tunnels and subways.

Seattle’s transit planners should stand back and rethink what they are doing as they will soon exhaust the taxpayer, funding an hybrid light rail/metro system that may ‘look cool’ but is very poor in attracting ridership.

As well, what is being advocated is not surface operation but elevated guide-ways, which are again, the hallmark of a light-metro.

What is really being advocated in Seattle is a grade separated transit system, either up in the air or underground, well out of the way of cars and trucks. Current ‘rail’ philosophy in Seattle is indeed very troublesome, hugely expensive, with very little customer appeal.

The key advantage of SkyTrain over Link is not ridership–Link is new and not well-built-out yet; were it to be more comprehensive it would attract more riders, as Seattle has good transit geography.

The advantage of SkyTrain is it’s driverless; allowing ridiculous frequency (every two minutes) at peak times for low cost. If anything, Seattle is missing an opportunity by not making Link driverless as well. Much of the system probably could be converted–the transit tunnel is the one place incompatible with driverless operation.

Whether or not Link ought to run all the way to Everett or Tacoma (or Olympia for that matter) is an interesting question–the distances involved are generally better served by Sounder-like systems. One advantage of light-rail is that if they DO do this, they can safely run the line at grade.

Of course the tunnel would be the most such incompatible. It should have been a rail tunnel in the first place, not a rail/bus tunnel. But there is one other place incompatible with automation on the Central Link. That’s the MLK Jr. Way segment.

If they fully grade separated the Central Link and made the downtown tunnel a true rail tunnel with no buses, then it would be a real metro.

Conversely, here in Ottawa, a Mecca of BRT with the Transitway, our proposed downtown transit tunnel will be light rail only and not “shared use” or a bus tunnel (and here in Ottawa, the downtown transit tunnel should use a Queen Street alignment, not the “zig zag” currently proposed). It should have 4 stations west of the Rideau Canal, not 2 as planned.

There simply isn’t any surface ROW between downtown and Northgate to use for rail transit, particularly if you want to serve the University of Washington and Capitol Hill along the way.

Sure the corridor could be served with a streetcar but that offers no real advantage over the existing bus service and in many ways is inferior as the streetcar couldn’t use the freeway.

There is also a capacity issue as surface LRT has problems with headways shorter than roughly 5 minutes which limits the capacity of any line with surface running segments. 9600 pphpd vs. the 24000 pphpd for the line being built. Given the already very high transit ridership in the corridor the extra capacity will be needed.

I know some aren’t big fans of speed but the 13 minute travel time between Northgate and Downtown or the 8 minutes between the University District and Downtown will be a major game changer. This beats SOV travel times even during periods of light traffic. This travel time savings will attract significant ridership all by itself.

Very little customer appeal? If anything, the effect should be the opposite. The grade separation between Lynnwood and Seattle will allow for travel times that actually rival SOV travel times. It is beyond me how you could possibly believe that a system that takes twice as long to travel the same distance (If built out like MLK or the MAX Yellow Line) could possibly have higher customer appeal than one that allows you to use the to travel the same distance in a competitive amount of time to a SOV.

Current ST projections estimate that the line, once built out, will have a daily weekday ridership close to 300,000 boardings a day. I fail to see how 300,000 boardings a day is “very poor ridership.” The ridership is that high precisely because of the grade separation, as it is much more attractive to a new transit user as it provides an alternative to driving without any major consequences (travel time is the same). This is not possible with the surface routes that you advocate.

SkyTrain has beggared the regional transit system. What is not generally known is that SkyTrain (not including the RAV/Canada Line) is subsidized annually by over $230 million by the provincial government; money that comes from schools hospitals and transit!

Being driverless means SkyTrain is very expensive to operate. Just the Expo Line costs 60% more to operate than the entire Calgary LRT line, which carries more people! Being driverless means high operating and maintenance costs and when there is a problem (and more problems are happening these days) the system shuts down at the most inappropriate times.

Many European tram systems operate at 1 minute or less frequencies during peak hours. Example: Karlsruhe Germany where 45 second headways are maintained during peak hours on the main street one can see an hourly ‘lift’ of over 30,000 pphpd!

What Seattle had got is a hybrid (read expensive) light rail/metro system that has attracted very few customers and seems very user unfriendly. For the money spent, Seattle should have got much better!

Jay, SkyTrain, being driverless doesn’t mean there is no one present on the metro system. Vancouver’s SkyTrain system has a large cadre of attendants who are on the train and at stations to maintain the integrity of the metro system. Added to this, we also have the SkyTrain police to counter increased crime on the metro system.

All driverless transit systems also maintain a Small army of electrical specialists, technicians and operators to keep the metro in operation. Unlike LRT, which has drivers, which can deal with small problems, on a driverless or automatic transit system, when a problem arises the metro stops until someone tell the computer it is safe to proceed. Sometimes this means an attendant must walk along the guide way to ensure there is no problem with the metro and is very time consuming.

SkyTrain has more employees (and higher operating costs) than LRT systems and what was once the flavour of the month in the 1980’s, is now reserved for the most heavily used metro lines in the world, where there are cost benefits with automatic operation.

Those who keep on proposing automatic metros for minor transit lines, really don’t know what they are talking about.

And they pay the price of higher subsidies to operate automatic or driverless subways. Dubai’s and Singapore’s automatic metro’s have been built more for political prestige than anything else (same is true with Vancouver’s SkyTrain). Copenhagen’s metro is so expensive to operate that transit planners what LRT instead bu the politicians win elections with driverless metro’s.

High maintenance costs are the Achilles heel of automatic operation and by having a driverless metro on a small routes means a penalty in having larger subsidies.

Only when ridership exceeds about 20,000 pphpd (Paris’s Meteor) is there a positive return on investment for automatic operating.

Both VAL and SkyTrain have been on the market for over 30 years, yet both have very high operating costs, which put them at a big disadvantage when competing against light rail.

The VAL mini-metro has lost consistently against LRT in France and only has been built when the central government paid/pays the difference. SkyTrain has been heavily subsidized by the Canadian Federal government which underwrites cheap loans for construction as which happened with the JFK AirTrain.

American transit expert Gerald Fox, wrote a paper some time ago, “A Comparison of AGT (Automatic Guided Transit) and LRT”, which documented why AGT cost more to operate.

Dubai’s and Singapore’s automatic metro’s have been built more for political prestige than anything else (same is true with Vancouver’s SkyTrain). Copenhagen’s metro is so expensive to operate that transit planners what LRT instead bu the politicians win elections with driverless metro’s.

Yes, yes, every city that builds LRT does so for rational reasons and every city that builds any other mode of transit does so for prestige.

I find that the article extremely biased and not very well researched, but hey, for the SkyTrain and automatic metro lobby that is the typical way of doing business.

Why then, despite after being on the market for over 30 years, only 7 SkyTrain systems has been built and not one has never been allowed to complete directly against light rail? To date SkyTrain has had at least five name changes (ICTS, ALRT (2 versions) ALM and ART and not one SkyTrain system has ever been allowed to compete directly against LRT for a transit project.

Funny that, during the same period of time over 100 new LRT systems have been built and an almost equal number are under construction or in the advanced stages of planning.

I’m sorry, but the “Dead Horse News”, certainly isn’t the transit forum I would think many transit experts would actually listen too. SkyTrain, VAL and many other proprietary light-metro systems (including monorail) have been made obsolete by LRT.

As for Calgary C-Train, carrying close to 300,000 passengers day, makes it the most successful light rail system in North America, so why not cite it as an example.

I’m not part of any lobby–nobody pays me to write anything, and my opinions are my own. If you read the article, you’ll notice I do address reasons why there aren’t many driverless metro systems in operation: they’re expensive to build, and politically difficult as well. Light rail is comparatively cheap to build, especially if you can run it alongside a freeway or in a boulevard median; and most North American cities lack either the density or the land-use patterns to support full metro. Most of the developed cities that can support metros have them already, and in the developing world, labor is sufficiently cheap that automation is out of the question.

I’m not a LRT opponent; I support it for Portland–a city where the local LRT system only achieves 1/3 the ridership of either Calgary or Vancouver, despite having more lane-miles (or lane-km) than either city. Here, the transit debate is LRT-vs-bus, and full metros are way off of anyone’s radar. If you had read the article, you’d know that as well.

You also seem to be conflating the name of TransLink’s metro system, with the various ATO/ATC systems in existence. To say “only seven SkyTrain systems have been built” is nonsensical, and there are at least 20 locales with driverless systems/lines–though quite a few of the examples listed are single-line (or even single-train) installations.

I give high praise to Calgary and C-Train (if you had read the article, you would have noted that as well)–my main point of mentioning C-Train is to note that its off-peak service suffers, whereas Vancouver can offer high-quality service during all hours of operation.

With regards to the quality (or lack thereof) of my blog–it, like most transit blogs, isn’t written by a transit professional. Nowhere do I claim otherwise. (Are you a transit professional, BTW, or an activist?) Transit professionals, of course, consult the professional literature of their field, not the amateur blogs of activists and hobbyists; and most professionals refrain from blogging themselves (Jarrett Walker at Human Transit being a notable exception). Jarrett, of course, has made his opinions on the subject clear; and the professional literature seems to look favorably on driverless metro–your favorite 1989 survey article notwithstanding.

To suggest that driverless metro is “obsoleted” by light rail, or vice versa, is nonsense. That’s like saying that BRT obsoletes light rail or streetcar–when in reality, they’re different technologies with different strengths and weaknesses, suitable for different applications. Falling in love with a particular mode or technology is generally a bad thing to do.